The invention relates to a control device for an asynchronous machine and a method for operating an asynchronous machine.
Document CH 477 124 A discloses an arrangement for controlling the slip frequency in an asynchronous machine.
Electric drives having induction machines excite different frequencies in the three-phase machine depending on the operating point which has been determined on the basis of the speed and torque, which can cause solid-borne or airborne noise to be output and the ripple of the output torque to be influenced. Resonances of the machine and/or the components coupled thereto, which can adversely influence the emitted airborne noise of the electric drive, occur in particular during the excitation of characteristic frequencies of the three-phase machine, for example, via the transfer of forces in the air gap between the stator and the rotor, or in the case of characteristic frequencies of the components which are flange-mounted on the drive shaft of the machine.
In certain speed ranges, characteristic frequencies are excited within the components of the electric drive by harmonic components of the three-phase machine, and the level of the emitted airborne noise increases abruptly at these characteristic frequencies. The noises emitted by an electric drive should be reduced to a minimum during operation, however.
Thus there is a need for solutions for the operation of asynchronous machines, in which the noise development can be kept to a minimum across the entire operating range without the need to substantially limit the design of the machine and its power density.